Data retransmissions in an anchor-booster network

ABSTRACT

Technology for performing data retransmissions is disclosed. An anchor evolved node B (eNB) can receive uplink control information from a user equipment (UE). The uplink control information can be transmitted in response to the UE receiving user data from a booster eNB. User data that is incorrectly received at the UE can be identified based on the uplink control information. The incorrectly received user data can be retransmitted directly from the anchor eNB to the UE independent of the booster eNB.

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional Patent Application No. 61/821,635, filed May 9, 2013 with a docket number of P56618Z, the entire specification of which is hereby incorporated by reference in its entirety for all purposes.

BACKGROUND

Wireless mobile communication technology uses various standards and protocols to transmit data between a node (e.g., a transmission station) and a wireless device (e.g., a mobile device). Some wireless devices communicate using orthogonal frequency-division multiple access (OFDMA) in a downlink (DL) transmission and single carrier frequency division multiple access (SC-FDMA) in an uplink (UL) transmission. Standards and protocols that use orthogonal frequency-division multiplexing (OFDM) for signal transmission include the third generation partnership project (3GPP) long term evolution (LTE), the Institute of Electrical and Electronics Engineers (IEEE) 802.16 standard (e.g., 802.16e, 802.16m), which is commonly known to industry groups as WiMAX (Worldwide interoperability for Microwave Access), and the IEEE 802.11 standard, which is commonly known to industry groups as WiFi.

In 3GPP radio access network (RAN) LTE systems, the node can be a combination of Evolved Universal Terrestrial Radio Access Network (E-UTRAN) Node Bs (also commonly denoted as evolved Node Bs, enhanced Node Bs, eNodeBs, or eNBs) and Radio Network Controllers (RNCs), which communicates with the wireless device, known as a user equipment (UE). The downlink (DL) transmission can be a communication from the node (e.g., eNodeB) to the wireless device (e.g., UE), and the uplink (UL) transmission can be a communication from the wireless device to the node.

In homogeneous networks, the node, also called a macro node, can provide basic wireless coverage to wireless devices in a cell. The cell can be the area in which the wireless devices are operable to communicate with the macro node. Heterogeneous networks (HetNets) can be used to handle the increased traffic loads on the macro nodes due to increased usage and functionality of wireless devices. HetNets can include a layer of planned high power macro nodes (or macro-eNBs) overlaid with layers of lower power nodes (small-eNBs, micro-eNBs, pico-eNBs, femto-eNBs, or home eNBs [HeNBs]) that can be deployed in a less well planned or even entirely uncoordinated manner within the coverage area (cell) of a macro node. The lower power nodes (LPNs) can generally be referred to as “low power nodes”, small nodes, or small cells.

In LTE, data can be transmitted from the eNodeB to the UE via a physical downlink shared channel (PDSCH). A physical uplink control channel (PUCCH) can be used to acknowledge that data was received. Downlink and uplink channels or transmissions can use time-division duplexing (TDD) or frequency-division duplexing (FDD).

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of the disclosure will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the disclosure; and, wherein:

FIG. 1 illustrates an anchor-booster network architecture in accordance with an example;

FIG. 2A is a table of non-ideal backhaul latencies with respect to various backhaul technologies in accordance with an example;

FIG. 2B is a table of ideal backhaul latencies with respect to various backhaul technologies in accordance with an example;

FIG. 3 illustrates a traditional hybrid automatic repeat request (HARQ) acknowledgement (ACK) and retransmission procedure at a booster evolved node B (eNB) in accordance with an example;

FIG. 4 is a hybrid automatic repeat request (HARQ) acknowledgement (ACK) and retransmission timing diagram of a traditional system in accordance with an example;

FIG. 5 is a hybrid automatic repeat request (HARQ) retransmission timing diagram in accordance with an example;

FIG. 6 illustrates a hybrid automatic repeat request (HARQ)-based retransmission scheme in accordance with an example;

FIG. 7 illustrates a protocol stack of a hybrid automatic repeat request (HARQ) retransmission scheme in accordance with an example;

FIG. 8 depicts functionality of computer circuitry of an anchor evolved node B (eNB) operable to perform data retransmissions in accordance with an example;

FIG. 9 depicts functionality of computer circuitry of a user equipment (UE) operable to receive data retransmissions in accordance with an example;

FIG. 10 depicts a flowchart of a method for performing data retransmissions in accordance with an example; and

FIG. 11 illustrates a diagram of a wireless device (e.g., UE) in accordance with an example.

Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.

DETAILED DESCRIPTION

Before the present invention is disclosed and described, it is to be understood that this invention is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular examples only and is not intended to be limiting. The same reference numerals in different drawings represent the same element. Numbers provided in flow charts and processes are provided for clarity in illustrating steps and operations and do not necessarily indicate a particular order or sequence.

Example Embodiments

An initial overview of technology embodiments is provided below and then specific technology embodiments are described in further detail later. This initial summary is intended to aid readers in understanding the technology more quickly but is not intended to identify key features or essential features of the technology nor is it intended to limit the scope of the claimed subject matter.

Heterogeneous networks have been widely regarded as a key technology for combating spectrum crunch and meeting wireless communication traffic growth in the years to come. Spectrum crunch can refer to user demand for data exceeding the spectrum bands and bandwidth available on current network infrastructures.

FIG. 1 illustrates an exemplary anchor-booster network architecture 100. The anchor-booster network architecture 100 is a form of heterogeneous network. The anchor-booster network architecture 100 includes at least one anchor evolved node B (eNB) 104 and at least one booster eNB 106. The anchor eNB 104 can be associated with an anchor cell, macro cell or primary cell. The booster eNB 106 can be associated with a booster cell, small cell or secondary cell. The booster eNB 106 can operate in the same or different frequency bands as the anchor eNB 104.

The anchor eNB 104 can be a high transmission power eNB for coverage and connectivity. The anchor eNB 104 is responsible for mobility because the coverage of the anchor eNB 104 is generally wider than that of the booster eNB 106. The anchor eNB 104 can also be responsible for radio resource control (RRC) signaling. The booster eNB 106 can be a low transmission power eNB for traffic offloading (i.e., offloading data transmissions) and quality of service (QoS) enhancement. The anchor eNB 104 and the booster eNB 106 can both serve packet data depending on the required QoS. For example, the anchor eNB 104 can serve delay sensitive data, such as Voice over IP (VoIP), while the booster eNB 106 services delay tolerant data, such as file transfer protocol (FTP).

A user equipment (UE) 108 can be supported by both the booster eNB 106 and the anchor eNB 104 in order to ensure mobility robustness, satisfy QoS performance and balance the traffic load between the anchor eNB 104 and the booster eNB 106. In other words, the UE 108 can support dual connectivity because the UE 108 is served by both the booster eNB 106 and the anchor eNB 104. With such dual connectivity, the anchor eNB 104 can handle control plane signaling and delay-sensitive traffic to the UE 108, while the booster eNB 106 can handle delay-tolerant user-plane traffic to the UE 108.

As shown in FIG. 1, the booster eNB 106 can be deployed under the coverage of the anchor eNB 104 and connected to the core network 102 via the anchor eNB 104. The anchor eNB 104 and the booster eNB 106 can be connected via an X2 interface. The anchor eNB 104 and the core network 102 can be connected via an S1 interface. The backhaul link connecting the anchor eNB 104 and the booster eNB 106 can be ideal or non-ideal. An ideal backhaul link can have a latency (in milliseconds) that is less than a predetermined value and a non-ideal backhaul link can have a latency that is greater than the predetermined value.

In traditional anchor-booster network architectures, once the traffic is split between the anchor eNB and the booster eNB, the data transmission procedures for the anchor eNB and the booster eNB are independent of each other. For example, the UE can receive VoIP data from the anchor eNB independent of receiving delay-tolerant data from the booster eNB. The independency in transmission does not fully exploit potential diversity gains in the anchor-booster network architecture. Moreover, when the backhaul latency between the anchor eNB and the booster eNB is non-ideal (i.e., the latency is greater than a predetermined value) and the UE does not support uplink carrier aggregation, the backhaul latency can impose further challenges to the anchor-booster network architecture.

Carrier aggregation (CA) enables multiple carrier signals to be simultaneously communicated between a user's wireless device and a node. Multiple different carriers can be used. In some instances, the carriers may be from different permitted frequency domains. Carrier aggregation provides a broader choice to the wireless devices, enabling more bandwidth to be obtained. The greater bandwidth can be used to communicate bandwidth intensive operations, such as streaming video or communicating large data files. Therefore, when the UE does not support uplink carrier aggregation, the UE cannot simultaneously communicate multiple carrier signals in the uplink.

In traditional systems where the UE does not support uplink carrier aggregation and the backhaul latency is non-ideal, the UE can only transmit uplink control information to the anchor eNB. The uplink control information can include hybrid automatic repeat request (HARQ) acknowledgement (ACK) and channel state information (CSI). HARQ is the simultaneous combination of Automatic Retransmission re-Quest (ARQ) and Forward Error Correction (FEC). HARQ enables the overhead of error correction to be adapted dynamically depending on the channel quality. When HARQ is used, if the errors can be corrected by FEC, then no retransmission is requested. If the errors can be detected but not corrected, a retransmission is requested. The CSI can describe characteristics of the radio channel. The CSI can include channel quality information (CQI), a pre-coding matrix indicator and a rank indicator.

The UE can transmit the uplink control information via PUCCH or physical uplink shared channel (PUSCH) to the anchor eNB. For example, the UE can indicate to the anchor eNB to retransmit data that was incorrectly received at the UE via the HARQ acknowledgement. The anchor eNB can serve as the primary eNB to ensure timely reception of the uplink feedback for scheduling the delay-sensitive traffic in the downlink.

If the physical downlink shared channel (PDSCH) is scheduled in the booster eNB, the anchor eNB needs to forward the HARQ and CSI information to the booster eNB in traditional systems. In traditional systems, only the booster eNB can retransmit data back to the UE. As the latency of the non-ideal backhaul between the anchor eNB and the booster eNB can be as high as tens of milliseconds, the delayed uplink control information (i.e., the HARQ and CSI) would cause high retransmission delay at the booster eNB, inefficient use of the booster eNB spectrum resources, and low UE peak data rates. In other words, since traditional anchor-booster network architectures only allow the UE to transmit the uplink control information to the anchor eNB, the delay in the anchor eNB forwarding the uplink control information to the booster eNB and then the booster eNB retransmitting the incorrectly received data back to the UE is prohibitive.

FIG. 2A is a table of non-ideal backhaul latencies with respect to various backhaul technologies. The term “non-ideal backhaul latency” generally refers to a time period (in milliseconds) that exceeds a predetermined value. Each backhaul technology can be associated with a latency (one-way), throughput and priority level. For example, fiber access 1 can have a latency of 10-30 ms, a throughput of 10M-10 Gigabits per second (Gbps) and a priority level of 1, wherein 1 is a highest priority level. Fiber access 2 can have a latency of 5-10 ms, a throughput of 100-1000 Megabits per second (Mbps) and a priority level of 2. Fiber access 3 can have a latency of 2-5 ms, a throughput of 50M-10 Gbps and a priority level of 1. Digital subscriber line (DSL) access can have a latency of 10-60 ms, a throughput of 10-100 Mbps and a priority level of 1. Cable can have a latency of 25-35 ms, a throughput of 10-100 Mbps and a priority level of 2. Wireless backhaul can have a latency of 5-35 ms, a throughput of 10-100 Mbps and a priority level of 1.

FIG. 2B is a table of ideal backhaul latencies with respect to various backhaul technologies. The term “ideal backhaul latency” generally refers to a time period (in milliseconds) that is less than a predetermined value. In one example, fiber can be a backhaul technology that has an ideal latency. In this example, the ideal latency (one-way) for fiber may not exceed 2.5 microseconds (μs) and the throughput may be 50M-10 Gbps.

FIG. 3 illustrates a traditional hybrid automatic repeat request (HARQ) acknowledgement (ACK) and retransmission procedure at a booster evolved node B (eNB). In step 1, the booster eNB can transmit data to the UE at T=0. In one example, the UE does not support uplink carrier aggregation. The UE can send uplink control information (e.g., HARQ and CQI) to the anchor eNB. The period of time for the uplink control information to be sent from the UE to the anchor eNB can be represented as T1. In other words, T1 can represent the latency when sending the uplink control information to the anchor eNB. In general, the latency refers to the period of time for information to be transmitted from one node to another node in the network. The HARQ in the uplink control information can indicate that the UE incorrectly received the data from the booster eNB. The anchor eNB can forward the uplink control information to the booster eNB. The period of time for the anchor eNB to forward the uplink control information to the booster eNB can be represented as Td. The booster eNB, upon receiving the uplink control information (e.g., HARQ) from the anchor eNB indicating that the UE incorrectly received the data, can retransmit the data to the UE. The period of time for the booster eNB to retransmit the data can be represented as T2. Therefore, the period of time between the UE receiving the incorrect data from the booster eNB (T=0) and the UE receiving the retransmitted data from the booster eNB can be relatively long and represented as T1+Td+T2.

As described in further detail below, the latency in retransmitting data can be reduced using a novel technique of retransmitting the incorrectly received data directly from the anchor eNB to the UE.

FIG. 4 is an exemplary hybrid automatic repeat request (HARQ) acknowledgement (ACK) and retransmission timing diagram 400 of a traditional system. The timing diagram 400 illustrates subframes when a booster eNB is transmitting (Tx) and subframes when HARQ is received at the booster eNB. The dashed frames shown in FIG. 4 can demonstrate the frame timing when the backhaul latency is ideal. The timing diagram 400 illustrates subframes that are used to transmit and retransmit data to the UE with respect to T1 which represents the time duration for the UE to send the uplink control information to the anchor eNB, Td which represents the time duration for the anchor eNB to forward the uplink control information to the booster eNB, and T2 which represents the time duration for the booster eNB to retransmit the data to the UE. The timing diagram 400 also illustrates subframes that are used to receive HARQ at the booster eNB.

In the example shown in FIG. 4, the booster eNB may transmit data that is incorrectly received at the UE in subframe “2,” but does not receive the HARQ until subframe “2,” which is approximately 15 subframes after transmitting the data. The booster eNB can retransmit the data in approximately four subframes (or four milliseconds). Therefore, the overall latency between the booster eNB initially transmitting the data and then retransmitting the data can be approximately 19 subframes. Although the example shown in FIG. 4 indicates a latency of approximately 19 subframes, the latency can vary depending on the type of backhaul link.

As previously explained, a relatively long round-trip time and eNB idle time can result due to the delayed HARQ acknowledgements. As a result, the UE QoS and peak data rate can be impaired, thereby harming the booster eNB spectrum and energy efficiency. Therefore, as described in further detail below, the anchor-booster network architecture with dual connectivity can support a novel HARQ retransmission scheme. The scheme can exploit the diversity gain of the anchor-booster network architecture and mitigate concerns arising from use of a non-ideal backhaul.

The novel HARQ retransmission scheme can support either the anchor eNB or the booster eNB retransmitting incorrectly received data to the UE in response to receiving the HARQ acknowledgement. One of the anchor eNB or the booster eNB can be selected to retransmit the data to the UE based on the backhaul latency (i.e., ideal or non-ideal) and whether the UE does or does not support uplink carrier aggregation.

In one example, the anchor eNB can retransmit the user data that was incorrectly received at the UE from the booster eNB, rather than forwarding the uplink control information to the booster eNB and then the booster eNB retransmitting the user data to the UE. As a result, the UE can receive the retransmission of the user data from the anchor eNB in less time (i.e., with lower latency), as compared to the UE receiving the retransmission of the user data from the booster eNB.

The anchor eNB can retransmit the user data to the UE instead of the booster eNB when the backhaul latency between the anchor eNB and the booster eNB is non-ideal (i.e., the backhaul latency exceeds a predetermined value). Alternatively, the anchor eNB can retransmit the user data to the UE instead of the booster eNB when the backhaul latency between the anchor eNB and the booster eNB is ideal (i.e., the backhaul latency is lower than a predetermined value). In addition, the anchor eNB may transmit the user data to the UE when the UE supports or does not support uplink carrier aggregation. In other words, the anchor eNB can retransmit the data even though the UE may or may not be able to support the communication of multiple uplink signals at substantially the same time. In order to ensure timely reception of the uplink feedback at the anchor eNB in supporting delay sensitive traffic, the anchor eNB can be used in handling the uplink traffic.

In one example, the UE receiving the data retransmission directly from the anchor eNB can result in a higher diversity gain and a lower latency as compared to receiving the data retransmission from the booster eNB. In addition, spectrum efficiency and peak data rate can be improved. The diversity gain may result from use of a different path in retransmitting the data packets that were received in error at the UE. In other words, using the path from the anchor eNB to the UE as opposed to reusing the path from the booster eNB to the UE can result in the diversity gain. Such multipath diversity can be beneficial for booster cells and can limit fading. Fading generally refers to a deviation of the attenuation affecting a signal, and as a result, can cause poor performance in a network because signal power can be lost without reducing the power of the noise. Slow fading can arise when a coherence time of the channel is relatively large as compared to the delay constraint of the channel. In addition, data retransmissions from the same transmission point in a relatively short time interval (i.e., the booster eNB sending the data and then resending the data) does relatively little to improve error performance.

The diversity gain resulting from the use of the different transmission path can prevent the likelihood of performing the data retransmission using an outdated CQI of the UE. For example, the anchor eNB may forward the UE's CQI to the booster eNB, but a change in network conditions can lead to the CQI being outdated, especially when the backhaul latency is relatively long. Therefore, the booster eNB may receive CQI information that is outdated and then perform the data retransmission using the outdated CQI, which could lead to performance degradation. When the anchor eNB retransmits the data to the UE instead of the booster eNB, the likelihood of using an outdated CQI is less because the time duration for retransmitting the data is less as compared to if the booster eNB were to retransmit the data.

When the backhaul latency is non-ideal and the UE does not support uplink carrier aggregation, the delay between two HARQ retransmissions can be relatively high. However, the diversity gain and improved error performance as described above can reduce the number of HARQ retransmissions. With a lower number of HARQ retransmissions due to the diversity gain and improved error performance, the associated latency can be reduced.

If the number of HARQ retransmissions were to remain the same, implementing the retransmissions at the anchor eNB can also lead to a lower delay because the retransmissions at the HARQ can be done in a successive manner due to timely reception of the HARQ acknowledgements. Therefore, the retransmission of the data from the anchor eNB as opposed from the booster eNB can result in a lower latency. On the other hand, when each of the retransmissions at the booster eNB are to wait for the delayed forwarding of HARQ acknowledgements, the time delay is increased.

FIG. 5 is an exemplary timing diagram 500 illustrating hybrid automatic repeat request (HARQ) retransmissions. The timing diagram 500 illustrates subframes that are used to transmit (Tx) data at a booster eNB, subframes used to receive HARQ-ACK at the anchor eNB, and subframes used to retransmit the data at the anchor. As shown in FIG. 5, the data retransmissions at the HARQ can be performed in a successive manner due to the timely reception of HARQ acknowledgements.

In the example shown in FIG. 5, the booster eNB can transmit data that is incorrectly received at the UE in subframe “2.” The anchor eNB can receive a NACK from the UE indicating that the data was incorrectly received approximately four subframes (or four milliseconds) after the booster eNB transmitted the data with the error. The anchor eNB can retransmit the data approximately four subframes after receiving the NACK from the UE. The anchor eNB can receive another NACK from the UE indicating that the data was incorrectly received a second time at the UE. The anchor eNB can retransmit the data approximately four subframes after receiving the second NACK from the UE. Since the anchor eNB retransmits the data directly to the UE upon receiving the HARQ, the overall latency can be reduced. Although the example shown in FIG. 5 indicates latencies of approximately four subframes between each communication, the latency can vary depending on the type of backhaul link.

In one configuration, the booster eNB can perform HARQ retransmissions (e.g., retransmissions of incorrectly received data) for the anchor eNB. For example, the anchor eNB may transmit data that is incorrectly received at the UE. Rather than the data being retransmitted by the anchor eNB, the booster eNB can retransmit the data to the UE in place of the anchor eNB. When the anchor eNB performs the retransmission for the booster eNB, data forwarding from the booster eNB to the anchor eNB is generally not required because user plane data for the booster eNB goes through the anchor eNB. In other words, the anchor eNB already holds the data that is to be retransmitted to the UE. On the other hand, when the booster eNB performs the retransmission for the anchor eNB, the booster eNB does not already hold the data that is to be retransmitted to the UE (i.e., the user plane data does not go through the booster eNB). Therefore, before the booster eNB can retransmit the data to the UE, the anchor eNB can forward the data to the booster eNB. Forwarding the data to the booster eNB can result in additional resource consumption at the backhaul link and increased delay when the backhaul link is non-ideal.

FIG. 6 illustrates an exemplary hybrid automatic repeat request (HARQ)-based retransmission scheme. In step 1, the booster eNB can transmit data to the UE at T=0. The data can be VoIP data, video data, etc. In one example, the UE does not support carrier aggregation in the uplink. In step 2, the UE can send uplink control information (e.g., HARQ and CQI) to the anchor eNB. The HARQ in the uplink control information can indicate that the UE incorrectly received the data from the booster eNB. The HARQ acknowledgements (i.e., the uplink control information) for the booster eNB can be transmitted in the PUCCH or PUSCH to the anchor eNB from the UE. The period of time for the uplink control information to be sent from the UE to the anchor eNB can be represented as T1. In other words, T1 can represent the latency when sending the uplink control information to the anchor eNB.

In step 3, upon the anchor eNB receiving the HARQ acknowledgement from the UE, the anchor eNB can perform the data retransmission in a timely manner. The period of time for the anchor eNB to retransmit the data to the UE can be represented as T4. Therefore, the period of time for the UE to send the HARQ acknowledgement indicating the incorrectly received data to the anchor eNB and for the anchor eNB to retransmit the data back to the UE can be represented as T1+T4.

Alternatively, in step 3, the anchor eNB can forward the uplink control information (e.g., CQI and HARQ) to the booster eNB. The period of time for the anchor eNB to forward the uplink control information to the booster eNB can be represented as T3. Therefore, the period of time for the booster eNB to receive the uplink control information from the UE, via the anchor eNB, can be represented as T1+T3. The booster eNB can retransmit the data to the UE upon receiving the HARQ acknowledgement from the anchor eNB.

The anchor eNB may identify a media access control (MAC) scheduling scheme of the booster eNB in order to determine the content for retransmission. In addition, the anchor eNB can determine the content for retransmission based on a channel condition or traffic load. The MAC scheduling scheme of the booster eNB can be inferred by the anchor eNB based on information sent from the booster eNB in the backhaul link. This information can include radio resource management (RRM) information at the booster eNB, such as a scheduled transport block (TB) size at the booster eNB, a radio link control (RLC) or media access control (MAC) protocol data unit (PDU), etc. Alternatively, the anchor eNB can identify the MAC scheduling scheme using information sent by the UE during an uplink transmission (e.g., the uplink control information).

In one example, the booster eNB can continue to send data packets to the UE or wait for the HARQ acknowledgements from the anchor eNB to continue its transmission. The booster eNB may act in accordance with the UE's capability. For example, the eNB can determine to continue sending data packets when the UE has sufficient buffering capability to support a relatively large number of HARQ processes. Otherwise, the booster eNB can determine to pause the transmission of data to the UE until receiving the HARQ acknowledgement (i.e., indicating that the data packet was successfully received at the UE). If the booster eNB waits to receive the HARQ acknowledgements, the booster eNB can schedule the released time slots in serving the other UEs or keep these time slots in idle. The scheduling of the released time slots in serving the other UEs can enhance spectrum efficiency at the booster eNB. In addition, the anchor eNB can perform scheduling with regards to the transmission of its own traffic, as well as aiding the booster eNB in performing data retransmissions in order to optimize the overall spectrum efficiency. In one example, the booster eNB can schedule its data transmission or data retransmission when the receipt of HARQ acknowledgements is delayed in order to optimize the spectrum efficiency and/or energy efficiency.

FIG. 7 illustrates an example S1-based protocol stack for a HARQ retransmission scheme. The S1-based protocol may include a packet data convergence protocol (PDCP) layer, Radio Link Control (RLC) layer, and a medium access control (MAC) layer that are associated with an anchor eNB. The anchor eNB may communicate media access channel (MAC) scheduling information and user-plane traffic HARQ/CQI to a booster eNB via an X2 interface.

The PDCP layer is the top sublayer of the LTE user plane layer 2 protocol stack. The PDCP layer processes Radio Resource Control (RRC) messages in the control plane and Internet Protocol (IP) packets in the user plane. Depending on the radio bearer, the main functions of the PDCP layer are header compression, security (integrity protection and ciphering), and support for reordering and retransmission during handover.

The RLC layer is located between the PDCP layer and the MAC layer in the LTE user plane protocol stack. The main functions of the RLC layer are segmentation and reassembly of upper layer packets in order to adapt the upper layer packets to a size appropriate for transmission over the radio interface. In addition, the RLC layer performs reordering to compensate for out-of-order reception due to Hybrid Automatic Repeat Request (HARQ) operation in the MAC layer.

The MAC layer is the protocol layer above the physical layer (PHY) and below the RLC layer in the LTE protocol stack. The MAC layer connects to the PHY through transport channels and connects to the RLC layer through logical channels. The MAC layer performs data transmission scheduling and multiplexing/demultiplexing between logical channels and transport channels.

In LTE, ciphering and integrity is used to protect data being received from a third party, or to detect changes made by the third party. In general, integrity refers to a receiver verifying that a received message is the same message as communicated by the transmitter/sender, whereas ciphering refers to the transmitter/sender encrypting the data with a security key that is known by the receiver. In the access stratum (AS) layer, ciphering and integrity are applied for RRC signaling data (i.e., control plane data) and only ciphering is applied for user data (i.e., user plane data or DRB data). The RRC layer is responsible for handling AS security keys and AS security procedure. In addition, the PDCP layer performs integrity and ciphering of the RRC signaling data, and ciphering of the user plane data.

Another example provides functionality 800 of computer circuitry of an anchor evolved node B (eNB) operable to perform data retransmissions, as shown in the flow chart in FIG. 8.

The functionality may be implemented as a method or the functionality may be executed as instructions on a machine, where the instructions are included on at least one computer readable medium or one non-transitory machine readable storage medium. The computer circuitry can be configured to receive uplink control information from a user equipment (UE) that is transmitted, to the anchor eNB, in response to the UE receiving user data from a booster eNB, as shown in block 810. The computer circuitry can be configured to determine a backhaul latency between the booster eNB and the anchor eNB relative to a selected threshold, as in block 820. The computer circuitry can be further configured to identify user data that is incorrectly received at the UE based on the uplink control information, as in block 830. In addition, the computer circuitry can be configured to retransmit the incorrectly received user data directly from the anchor eNB to the UE independent of the booster eNB when the backhaul latency is greater than the selected threshold, as in block 840.

In one example, the computer circuitry can be further configured to retransmit the incorrectly received user data to the UE when the UE does not support uplink carrier aggregation. In addition, the computer circuitry can be further configured to retransmit the incorrectly received user data to the UE when the UE does support uplink carrier aggregation. Furthermore, the computer circuitry can be configured to retransmit the incorrectly received user data to the UE when the backhaul latency is less than the selected threshold. In one example, the uplink control information includes hybrid automatic repeat request (HARQ)-acknowledgement (ACK) and channel state information (CSI) associated with the user data that is incorrectly received at the UE from the booster eNB.

In one configuration, the computer circuitry can be further configured to retransmit the incorrectly received user data to the UE based on a channel condition received in the uplink control information, a traffic load at the anchor eNB and a medium access control (MAC) scheduling scheme of the booster eNB. In addition, the computer circuitry can be further configured to infer the MAC scheduling scheme of the booster eNB using information sent from the booster eNB in the backhaul link or the uplink control information received from the UE. Furthermore, the computer circuitry can be configured to schedule data transmissions from the anchor eNB and data retransmissions performed at the anchor eNB for the booster eNB in order to optimize spectrum efficiency.

In one example, the anchor eNB supports delay-sensitive control-plane traffic and the booster eNB supports delay-tolerant user-plane traffic. The computer circuitry can be further configured to send HARQ acknowledgements to the booster eNB, wherein the booster eNB resumes sending data packets to the UE upon receiving the HARQ acknowledgements from the anchor cell. In addition, the computer circuitry can be further configured to retransmit the incorrectly received user data to the UE independent of the booster eNB in order to increase multipath diversity. In one example, the anchor eNB is a macro eNB and the booster eNB is a low power eNB.

Another example provides functionality 900 of computer circuitry of a user equipment (UE) operable to receive data retransmissions, as shown in the flow chart in FIG. 9. The functionality may be implemented as a method or the functionality may be executed as instructions on a machine, where the instructions are included on at least one computer readable medium or one non-transitory machine readable storage medium. The computer circuitry can be configured to receive user data from a booster evolved node B (eNB), as shown in block 910. The computer circuitry can be configured to send uplink control information to an anchor eNB, the uplink control information indicating incorrectly received user data at the UE, as shown in block 920. The computer circuitry can be further configured to receive a retransmission of the incorrectly received user data directly from the anchor eNB independent of the booster eNB, as shown in block 930.

In one configuration, the computer circuitry is further configured to receive the retransmission of the incorrectly received user data from the anchor eNB independent of the booster eNB when a backhaul latency between the booster eNB and the anchor eNB is greater than a selected threshold. In addition, the computer circuitry is further configured to receive the retransmission of the incorrectly received user data from the anchor eNB when the UE does not support uplink carrier aggregation. In one example, the uplink control information includes a hybrid automatic repeat request (HARQ)-acknowledgement (ACK) and channel state information (CSI) associated with the incorrectly received user data. The computer circuitry is further configured to receive the retransmission of the incorrectly received user data from the booster eNB when a backhaul latency between the booster eNB and the anchor eNB is greater than a selected threshold. In addition, the UE includes an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, an internal memory, or a non-volatile memory port.

Another example provides a method 1000 for performing data retransmissions, as shown in the flow chart in FIG. 10. The method may be executed as instructions on a machine, where the instructions are included on at least one computer readable medium or one non-transitory machine readable storage medium. The method includes the operation of receiving uplink control information, at an anchor evolved node B (eNB) from a user equipment (UE), the uplink control information being transmitted in response to the UE receiving user data from a booster eNB, as shown in block 1010. The method includes the operation of identifying user data that is incorrectly received at the UE based on the uplink control information, as shown in block 1020. The method further includes the operation of retransmitting the incorrectly received user data directly from the anchor eNB to the UE independent of the booster eNB, as shown in block 1030.

In one configuration, the method includes determining a backhaul latency between the booster eNB and the anchor eNB relative to a selected threshold; and retransmitting the incorrectly received user data directly from the anchor eNB to the UE independent of the booster eNB when the backhaul latency is greater than the selected threshold. In addition, the method includes determining that the backhaul latency between the booster eNB and the anchor eNB is less than the selected threshold; and forwarding the uplink control information to the booster eNB to enable the booster eNB to retransmit the incorrectly received user data to the UE. Furthermore, the method includes retransmitting the incorrectly received user data to the UE based on a channel condition received in the uplink control information, a traffic load at the anchor eNB and a medium access control (MAC) scheduling scheme of the booster eNB. In one example, the UE includes an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, an internal memory, or a non-volatile memory port.

FIG. 11 provides an example illustration of the wireless device, such as an user equipment (UE), a mobile station (MS), a mobile wireless device, a mobile communication device, a tablet, a handset, or other type of wireless device. The wireless device can include one or more antennas configured to communicate with a node, macro node, low power node (LPN), or, transmission station, such as a base station (BS), an evolved Node B (eNB), a baseband unit (BBU), a remote radio head (RRH), a remote radio equipment (RRE), a relay station (RS), a radio equipment (RE), or other type of wireless wide area network (WWAN) access point. The wireless device can be configured to communicate using at least one wireless communication standard including 3GPP LTE, WiMAX, High Speed Packet Access (HSPA), Bluetooth, and WiFi. The wireless device can communicate using separate antennas for each wireless communication standard or shared antennas for multiple wireless communication standards. The wireless device can communicate in a wireless local area network (WLAN), a wireless personal area network (WPAN), and/or a WWAN.

FIG. 11 also provides an illustration of a microphone and one or more speakers that can be used for audio input and output from the wireless device. The display screen may be a liquid crystal display (LCD) screen, or other type of display screen such as an organic light emitting diode (OLED) display. The display screen can be configured as a touch screen. The touch screen may use capacitive, resistive, or another type of touch screen technology. An application processor and a graphics processor can be coupled to internal memory to provide processing and display capabilities. A non-volatile memory port can also be used to provide data input/output options to a user. The non-volatile memory port may also be used to expand the memory capabilities of the wireless device. A keyboard may be integrated with the wireless device or wirelessly connected to the wireless device to provide additional user input. A virtual keyboard may also be provided using the touch screen.

Various techniques, or certain aspects or portions thereof, may take the form of program code (i.e., instructions) embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, non-transitory computer readable storage medium, or any other machine-readable storage medium wherein, when the program code is loaded into and executed by a machine, such as a computer, the machine becomes an apparatus for practicing the various techniques. Circuitry can include hardware, firmware, program code, executable code, computer instructions, and/or software. A non-transitory computer readable storage medium can be a computer readable storage medium that does not include signal. In the case of program code execution on programmable computers, the computing device may include a processor, a storage medium readable by the processor (including volatile and non-volatile memory and/or storage elements), at least one input device, and at least one output device. The volatile and non-volatile memory and/or storage elements may be a RAM, EPROM, flash drive, optical drive, magnetic hard drive, solid state drive, or other medium for storing electronic data. The node and wireless device may also include a transceiver module, a counter module, a processing module, and/or a clock module or timer module. One or more programs that may implement or utilize the various techniques described herein may use an application programming interface (API), reusable controls, and the like. Such programs may be implemented in a high level procedural or object oriented programming language to communicate with a computer system. However, the program(s) may be implemented in assembly or machine language, if desired. In any case, the language may be a compiled or interpreted language, and combined with hardware implementations.

It should be understood that many of the functional units described in this specification have been labeled as modules, in order to more particularly emphasize their implementation independence. For example, a module may be implemented as a hardware circuit comprising custom VLSI circuits or gate arrays, off-the-shelf semiconductors such as logic chips, transistors, or other discrete components. A module may also be implemented in programmable hardware devices such as field programmable gate arrays, programmable array logic, programmable logic devices or the like.

Modules may also be implemented in software for execution by various types of processors. An identified module of executable code may, for instance, comprise one or more physical or logical blocks of computer instructions, which may, for instance, be organized as an object, procedure, or function. Nevertheless, the executables of an identified module need not be physically located together, but may comprise disparate instructions stored in different locations which, when joined logically together, comprise the module and achieve the stated purpose for the module.

Indeed, a module of executable code may be a single instruction, or many instructions, and may even be distributed over several different code segments, among different programs, and across several memory devices. Similarly, operational data may be identified and illustrated herein within modules, and may be embodied in any suitable form and organized within any suitable type of data structure. The operational data may be collected as a single data set, or may be distributed over different locations including over different storage devices, and may exist, at least partially, merely as electronic signals on a system or network. The modules may be passive or active, including agents operable to perform desired functions.

Reference throughout this specification to “an example” means that a particular feature, structure, or characteristic described in connection with the example is included in at least one embodiment of the present invention. Thus, appearances of the phrases “in an example” in various places throughout this specification are not necessarily all referring to the same embodiment.

As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as defacto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided, such as examples of layouts, distances, network examples, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, layouts, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below. 

1. An anchor evolved node B (eNB) operable to perform data retransmissions, the anchor eNB having computer circuitry configured to: receive uplink control information from a user equipment (UE) that is transmitted, to the anchor eNB, in response to the UE receiving user data from a booster eNB; determine a backhaul latency between the booster eNB and the anchor eNB relative to a selected threshold; identify user data that is incorrectly received at the UE based on the uplink control information; and retransmit the incorrectly received user data directly from the anchor eNB to the UE independent of the booster eNB when the backhaul latency is greater than the selected threshold.
 2. The computer circuitry of claim 1, further configured to retransmit the incorrectly received user data to the UE when the UE does not support uplink carrier aggregation.
 3. The computer circuitry of claim 1, further configured to retransmit the incorrectly received user data to the UE when the UE does support uplink carrier aggregation.
 4. The computer circuitry of claim 1, further configured to retransmit the incorrectly received user data to the UE when the backhaul latency is less than the selected threshold.
 5. The computer circuitry of claim 1, wherein the uplink control information includes hybrid automatic repeat request (HARQ)-acknowledgement (ACK) and channel state information (CSI) associated with the user data that is incorrectly received at the UE from the booster eNB.
 6. The computer circuitry of claim 1, further configured to retransmit the incorrectly received user data to the UE based on a channel condition received in the uplink control information, a traffic load at the anchor eNB and a medium access control (MAC) scheduling scheme of the booster eNB.
 7. The computer circuitry of claim 5, further configured to infer the MAC scheduling scheme of the booster eNB using information sent from the booster eNB in the backhaul link or the uplink control information received from the UE.
 8. The computer circuitry of claim 1, further configured to schedule data transmissions from the anchor eNB and data retransmissions performed at the anchor eNB for the booster eNB in order to optimize spectrum efficiency.
 9. The computer circuitry of claim 1, wherein the anchor eNB supports delay-sensitive control-plane traffic and the booster eNB supports delay-tolerant user-plane traffic.
 10. The computer circuitry of claim 1, further configured to send HARQ acknowledgements to the booster eNB, wherein the booster eNB resumes sending data packets to the UE upon receiving the HARQ acknowledgements from the anchor cell.
 11. The computer circuitry of claim 1, further configured to retransmit the incorrectly received user data to the UE independent of the booster eNB in order to increase multipath diversity.
 12. The computer circuitry of claim 1, wherein the anchor eNB is a macro eNB and the booster eNB is a low power eNB.
 13. A user equipment (UE) operable to receive data retransmissions, the UE having computer circuitry configured to: receive user data from a booster evolved node B (eNB); send uplink control information to an anchor eNB, the uplink control information indicating incorrectly received user data at the UE; and receive a retransmission of the incorrectly received user data directly from the anchor eNB independent of the booster eNB.
 14. The computer circuitry of claim 13, further configured to receive the retransmission of the incorrectly received user data from the anchor eNB independent of the booster eNB when a backhaul latency between the booster eNB and the anchor eNB is greater than a selected threshold.
 15. The computer circuitry of claim 13, further configured to receive the retransmission of the incorrectly received user data from the anchor eNB when the UE does not support uplink carrier aggregation.
 16. The computer circuitry of claim 13, wherein the uplink control information includes a hybrid automatic repeat request (HARQ)-acknowledgement (ACK) and channel state information (CSI) associated with the incorrectly received user data.
 17. The computer circuitry of claim 13, further configured to receive the retransmission of the incorrectly received user data from the booster eNB when a backhaul latency between the booster eNB and the anchor eNB is greater than a selected threshold.
 18. The computer circuitry of claim 13, wherein the UE includes an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, an internal memory, or a non-volatile memory port.
 19. A method for performing data retransmissions, the method comprising: receiving uplink control information, at an anchor evolved node B (eNB) from a user equipment (UE), the uplink control information being transmitted in response to the UE receiving user data from a booster eNB; identifying user data that is incorrectly received at the UE based on the uplink control information; and retransmitting the incorrectly received user data directly from the anchor eNB to the UE independent of the booster eNB.
 20. The method of claim 19, further comprising: determining a backhaul latency between the booster eNB and the anchor eNB relative to a selected threshold; and retransmitting the incorrectly received user data directly from the anchor eNB to the UE independent of the booster eNB when the backhaul latency is greater than the selected threshold.
 21. The method of claim 20, further comprising: determining that the backhaul latency between the booster eNB and the anchor eNB is less than the selected threshold; and forwarding the uplink control information to the booster eNB to enable the booster eNB to retransmit the incorrectly received user data to the UE.
 22. The method of claim 19, further comprising retransmitting the incorrectly received user data to the UE based on a channel condition received in the uplink control information, a traffic load at the anchor eNB and a medium access control (MAC) scheduling scheme of the booster eNB.
 23. The method of claim 19, wherein the UE includes an antenna, a touch sensitive display screen, a speaker, a microphone, a graphics processor, an application processor, an internal memory, or a non-volatile memory port.
 24. At least one non-transitory machine readable storage medium comprising a plurality of instructions adapted to be executed to implement the method of claim
 19. 